The places are generalized references to data
upon which test-form depends,
whose values can be changed by the user in attempting to correct the error.
Subforms of each place are only evaluated if an error is signaled,
and might be re-evaluated if the error is re-signaled (after continuing without
actually fixing the problem).
The order of evaluation of the places is not specified;
see Section 5.1.1.1 Evaluation of Subforms to Places.
If a placeform is supplied that produces more values than there
are store variables, the extra values are ignored. If the supplied
form produces fewer values than there are store variables,
the missing values are set to nil.

The debugger need not include the test-form in the error message,
and the places should not be included in the message, but they
should be made available for the user's perusal. If the user gives the
"continue" command, the values of any of the references can be altered.
The details of this depend on the implementation's style of user interface.